Heating panel



April 17, 1956 H. P. BOVENKERK HEATING PANEL Filed Oct. 14, 1952 Invent/GTT Harold F Bovehkerk, by /M/ 734%/ Hs Attorney.

United States Patent C) i HEATING PANEL Harold P. Bovenkerk, Ballston Lake, N. Y., assignor to General Electric Company, a corporation of New York Application October 14, 1952, Serial No. 314,638

11 Claims. (Cl. 219-19) This invention relates to a heating panel suitable for heating a room; more particularly, the invention relates to a heating panel suitable for use as a wall structural member having incorporated therein a resistance heating element which will heat a room economically by electricity.

For many years, space heaters utilizing an electric resistance heating element have been in use. Formerly, such heaters consisted of a parabolic reflecting surface in the center of which was mounted a coiled section of Nichrome wire. More recently, such heaters have omitted the reflecting surface but operate in conjunction with an electric fan which blows air to be heated past the element. Other space heaters of recent years have included a waterreservoir to temper the action of the heating element. While space heating by electrical resistance elements has many attractive features,.in most localities the cost of electric power is high enough to make the cost of heating the ordinary house by electrical space heaters of the resistance type prohibitive.

Accordingly, it is an object of this invention to provide a resistance heater built into a wall panel having such effective thermal insulation that electrical space heating becomes economically feasible.

It is another object of this invention to provide a heating panel which is highly unidirectional with reference to heat flow.

YIt is another object of the invention to provide a heating panel suitable for incorporation as a structural member in a wall.

It isa further object of the invention to provide a thermally insulated radiant heat panel utilizingtwo types of thermal insulation to provide the bestV insulated panel at 1the lowest cost.

l Briey stated, in accordance with one of its aspects, this invention comprises a wall heating panel having a front and back metal surface in spaced relation, an electric heatingelemen't in the space between the surfaces adjacent the front metal "surface and electrically insulated from the front metal surface, a blanket of temperature stable material overlying the heating element, and a blanket of mineral insulating fibers positioned in the space between the blanket of temperature stable material and the back metal surface.

Fig. l of the drawing is a broken sectional view of la heating panel made in accordance with this invention. Fig. 2 is a broken sectional view of an alternative panel construction.

A front metal surface and a spaced back metal surface 11 are in gas-tight sealed engagement around their edges as by a weld 12. The metal of which the surfaces 10 and 11 are composed is preferably of a type offering high resistance to the diffusion of gases therethrough. Alloys are also satisfactory .for this purpose. The metal of which the surface l11 is composed should preferably have a low coefiicient of thermal conductivity, but this is not necessary in the case of the surface 10 since, as will be subsequently explained herein, it serves 2,742,556 yPatented Apr. 17,

as a surface for the radiation of heat. Stainless steel and corrosion-resistant alloys such as Monel metal (an alloy containing copper and nickel) are satisfactory construction" materials for the panel. Carbon steel is also satisfactory provided it is given a protective covering such as baked enamel or a coating of resin in order to prevent rusting, If the surface 10 is composed of carbon steel, the protective coating applied must be temperature-stable. Porcelain enamel will provide the necessary degree of temperature stability.

The surfaces 10 and 11 are spaced to define a chamber 13 which is mainted at a pressure of lessthan one millimeter mercury and preferably at a pressure of the order of ten to one hundred microns mercury. The front surface 10 is lined with an insulating material 14 such as mica or cloth made of silicon dioxide bers. The layer of insulating material 14 serves the purpose of electrically insulating the metal surface 10 from a resistance heating element 15. Thus, any form of electrical insulation which would not destroy the vacuum of the chamber 13 would be a suitable substitute for the silicon dioxide or mica previously set forth as the composition of the material 14.

Theheating element 15 is connected by means of lead wires 17 to a pair` of electrodes 16 which pass in sealed engagement through a glass or ceramic element 18 which is in turn sealed in gas-tight engagement by means of a glass-metal seal 19 to a nipple 20 mounted on the metal surface 11.

A blanket of heat stable material 21 is positioned in back of the resistance heating element 15. The blanket 21 must be composed of material which is stable under the high temperature to which the element 15 is heated. Materials suitable for this purpose are aluminum oxide powder, aluminum oxide fibers, high-melting slag wool, mica, and silicon dioxide granules or fibers.`

Occupying the space within the chamber 13 between the blanket 21 and back metal surface 11 is a blanket 22 of mineral insulating fibers such as glass wool or slag wool. It is not necessary that the blanket 22 have great stability at the temperature at which the heating element 15 operates since the blanket 21 protects the blanket 22 from the high temperature. ln carrying out this invention, I prefer to form the blanket 21 of silicon dioxide fibers and the blanket 22 of glass fibers and to have the blanket 22 occupying most of the space 13. Normally this will be over half the thickness of the panel. Glass fibers have insulating qualities equal to silicon dioxide fibers but cost less. Thus, by forming a mineral fiber laminate of the type illustrated, I obtain the best insulation at the lowest cost.

I preferto form the blanket 22 of glass fibers after the manner disclosed and claimed by Strong and Bundy in application Serial No. 236,788, filed July 14, 1951, and assigned to the same assignee as the present application.

The Strong and Bundy application discloses that superior heat vinsulation can be obtained if the individual fibers of are generally perpendicular to the direction of heat transfer through the panel.- p It is preferable that vthe individual fibers have a diameter of less than one-thousandth of an inch and that the fibers be packed to a densityin excess of ten pounds per cubic foot. In general, the finer the fibers, the better the insulation and the lessv dense the fibers have to be packed in ordery to provide goodinsulating qualities. There is noA critical range of liber size or blanket density nor is there a critical pressure 'range'. 'at which the chamber 13 must be maintained. The panel is an effective heating device 'at atmospheric'pressure with fibers of a diameter greater than one-thousandth of an' strip 25 lto seal the edges of the panels.

inch packed to a density of less than ten pounds per cubic foot. Nevertheless, as the pressure and fiber diameter are decreased, and as the blanket density is increased, the heating and insulating qualities of the device are improved. It is to be understood that I do not herein claim as my invention anything shown lor described in said Strong and Bundy application, which is to be regarded as priorl art with respect to the present application.

The back metal surface 11 has mounted thereon an evacuation port 23 which is connected to a vacuum pump (not shown) during fabrication of the panel. ln constructing the panel, I prefer to precompact the blanket of glass fibers in accordance with the method disclosed and claimed in J anos application, Serial No. 23 6,971, filed July 16, 1951, and assigned to the same assignee as the present application. In the structure of the J anos application, a blanket of glass fibers is compressed to the density desired for use, and while compressed, the blanket is heated to a temperature just below the softening point of the glass fibers. The compressive force is then removed after the blanket has cooled. The blanket then retains its compressed shape.

During the evacuation process, it is necessary that the mineral substances be heated in order to drive off occluded gases. This may be accomplished by connecting the electrodes 16 to a source of energy and utilizing the heating element 15 to bring the panel up to out-gassing temperature. This is done in addition to heating the entire panel in an oven. The heating element is outgassed at a higher temperature as it must operate ata higher temperature.

When the interior pressure of the panel is of the order of one millimeter mercury, the pressure against the sides of the panel is of the order of two thousand pounds per square foot. This pressure produces a very rigid structure even though the metal surfaces and 11 are comparatively thin. Even a thin panel makes a satisfactory structural member in house or factory construction.

Fig. 2 illustrates apanel construction utilizing abreaker Such a construction diminishes the loss of heat along the edges of the panels.

During operation, the panel is preferably mounted on a wall. When the heating element is energized the blankets 21 and 22 serve as reectors directing the radiant heat toward the front surface 10 which intercepts the radiant energy and transfers it by conduction'to a uniform level throughout the surface which then radiates the heat through the room. Thus, the high temperature radiant energy from the element 15 is converted to low temperature radiant energy from the surface 10. Low energy radiant heat is much more comfortable to the occupants of the room.

During operation the back metal surface 11 remains cool. There is almost no heat loss through this surface from conduction, convection, or radiation.

While the present invention has been described with reference to particular embodiments; thereof, it will be understood that numerous modifications `may be made by those skilled in the art withoutactually departing from the invention. Therefore, I aim in the appended claims to cover all such equivalent variations as come within the true spirit and scope of the foregoing disclosure.

What I claim as new and desire to Vsecure by Letters Patent of the United States is:

1. A wall heating panel comprising a front and back metal Asurface sealed in gas-tight spaced relation and defining an evacuated space, an electrical heating element positioned in Asaid evacuated space adjacent -said front surface, a lblanket of silicon dioxide fibers overlying said heating element, and a blanket of mineral insulating fibers occupying the evacuated space Abetween said blanket of silicon dioxide fibers and said back metal surface.

2. A wall heating panel comprising a front metal sheet and a back metal sheet in gas-tight spaced relation defining an evacuated space, an electrical heatingv element positioned in said evacuated space adjacent said front metal sheet, a silicon dioxide fiber blanket overlying'said heating element, and a blanket of mineral insulating fibers occupying the evacuated space between said silicon dioxide fiber blanket and said back metal sheet.

3. A heating panel for positioning on a wall comprising a front and back metal sheet in gas-tight sealed spaced relation forming an envelope dening an evacuated space of substantially uniform thickness, a layer of heat stable electrically insulating material lining said front metal sheet in said evacuated space, an electrical heating kelement in contact with said electrically insulating material, a blanket of silicon dioxide fibers `overlying said heating element, and a blanket of mineral insulating fibers occupying the evacuated space between said blanket of silicon dioxide fibers and said back metal sheet, said blanket of insulating fibers being over half as thick as the evacuated space in which it is positioned.

4. A heating panel comprising an envelope dening an evacuated space formed of a pair of spaced metal sheets in gas-tight sealed engagement around their edges, one of said sheets constituting the front of said panel and the other the back, an electric heating element in said envelope adjacent the front metal sheet but electrically insulated therefrom, a blanket of silicon dioxide fibers overlying said heating element, and a blanket of glass fibers positioned between said silicon dioxide fibers and the back metal sheet.

5. A heating panel comprising an envelope defining an evacuated space formed of a pair of spaced metal sheets in gas-tight sealed engagement around their edges, the pressure in said evacuated space being less than 1 mm. Hg, one or" said sheets constituting the front of said panel and the other the back, an electric heating element in said envelope adjacent the front metal sheet but electrically insulated therefrom, a blanket of temperature stable heat insulating fibers overlying said heating element, and a blanket of glass fibers positioned between said heat insulating fibers and the back metal sheet.

6. A heating panel comprising an envelope defining an evacuated space formed of a pair of spaced metal sheets in gas-tight sealed engagement around their edges, one of said sheets constituting the front of said panel and the other the back, an electric heating element in said envelope adjacent the front sheet but electrically insulated therefrom, a blanket of temperature stable heat insulating fibers overlying said heating element, and a blanket of glass fibers positioned between said heat insulating fibers and the back metal sheet, said glass bers having a diameter of less than one-thousandth of an inch.

7. A heating panel comprising a front and back metal sheet in gas-tight sealed spaced relation forming an envelope defining an evacuated space, an electric heating element in said evacuated space adjacent the front 'metal sheet, a blanket of mineral fibers selected from the Vgroup consisting of silicon dioxide and aluminum oxide yover said heating element, and a blanket of glass fibers between said lfirst-mentioned blanket of fibers and said back metal sheet.

v8. A heating panel as claimed in claim 7 wherein `the blanket of mineral fibers over the heating element is composed of silicon dioxide fibers.

9. A heating panel comprising a front and back metal sheet in gas-tight vsealed spaced relation forming `an envelope defining an evacuated space, an electric heating element in said evacuated space adjacent to, but electrically insulated from, said front metal sheet, a blanket of temperature stable heat insulating material behind said heating element, and a blanket of glass fibers between said temperature stable material and said back 'nr'etal sheet, said blanket of glass fibers being compressed `to a vdensity in excess of ten pounds per cubic foot.

l0. A heating panel as claimed in claim 9 wherein the individual fibers of the blanket of glass fibers have their axes randomly oriented in planes generally parallel to the surface planes of the panel.

11. A heating panel comprising a front and back metal sheet in gas-tight sealed spaced relation forming an envelope defining a space of approximately uniform thickness in which the pressure is less than 1 mm. Hg, a cloth of silicon dioxide lbers lining said front metal sheet Within said space, an electric heating element positioned in Contact with said cloth, a backing layer of silicon dioxide bers in contact with said heating element, and a blanket of glass fibers between said backing layer and said back metal sheet, said blanket being compressed to a density in excess of ten pounds per cubic foot and the individual bers of said blanket being randomly oriented in planes generally parallel to the surface planes of the panel.

References Cited in the le of this patent UNITED STATES PATENTS Edwards Feb. 5, 1895 Morey Feb. 1l, 1941 Devers Aug. 11, 1942 Ackley Mar. 14, 1950 Mossin Apr. 18, 1950 Hoffmann Apr. 25, 1950 Briscoe et al Oct. 23, 1951 Myers Nov. 27, 1951 FOREIGN PATENTS Great Britain June 30, 1947 

